does anybody's CB suffer bad interferance when the engine is running. I get great reception and distance with the engine off but when it's running I practically have to be right beside the person to talk to them. Anybody have any suggestions. Thanks.

 

[updated:LAST EDITED ON 25-Oct-02 AT 10:55 PM (EST)]i have the same problem in my truck. at first i thought it was dirty power so i put in a heavy duty power filter. no change in symptoms. i ripped that out confused as to what to do next. a buddy of mine reccomended running the power for the radio straight off the battery. that seemed to help somewhat, but not completely. if i turn my rf gain on my radio a little higher i hear the engine noise so it is still there. i am still looking for a fix though. i have noticed however that in my buddys truck he does not have that problem. his truck has the big bad 351. i have 300 I6, and hear the engine noise.
if anyone knows how to fix this i would greatly appreciate any info.

 

Fuel injected Fords have "noisey"electric fuel pumps.Ford sells an electronic filter to help,but you probably will have to drop the gas tank to install it. Also,it's not cheap.

 

I will get the part number of this filter and post back with the price from Ford.

 

Ok, I called around to several dealers and heres the info i got. Ford part # F1PZ18B925A , price $59.95. You do not have to drop the tank. And you do not need two if you have dual tanks. The part is a power filter that goes in line with the power wires to the high pressure pump mounted on the frame rail. Of the two dealers i called niether one had one in stock. the second dealer did a check in my area (san Diego) and only 1 dealer had 1 in stock. I am going to look in this a little further. If it is a basic power filter then a trip to radio shack might be the cure. I have bought a heavy duty power filter from them before but not for this application. And it only cost 10 bucks. I will keep y'all posted on my progress. I really hate that noise in my CB.

 

[updated:LAST EDITED ON 31-Dec-02 AT 04:13 PM (EST)]Can't you just put a good size capacitor across the leads of the fuel pump? All your trying to do is get rid of the AC current, a cap will do that. I doubt radioshack will have one big enough. A trip to the appliance repair shop may be in order, I don't know. Better yet, why not a cap across the pos and neg wires of the cb unit? That will filter any AC current out of the power input into the cb.

I almost forgot, you will need an UNPOLARIZED capacitor. Be sure of this. If the cap you have has a '+' on one lead and '-' on the other, it is polarized, don't use it.

Just another note of confidence, in radio controlled cars, the motors have 2 caps acoss the leads, else it will interfere with proper control. Check it out.

 

The part listed above works great and is the only thing I have found to work properly. I'm sure a cap will work also, but you want to put it on the fuel pump wires. If you put it inline with the radio power, you will still get interference through your coax. I have 3 in my X - one on the fuel pump, one on the MSD DIS4, and one on my Stinger power distribution block and ground block. Got rid of all the noise...

 

How do you get noise through all the sheilding in coax? Coax is some of the most sheilded means of transporting signal, with all that tight braided wire that surrounds the core. Unless the sheilding is not grounded. It could be coming in at the antenna however. Make sure the antenna circuit is not part of the car body. None of the wires from the antenna nor the antenna itself should be touching any metal.

If the antenna is not touching the body, the sheilding in the coax is grounded, and the power supply for the cb is clean, I don't see how noise could be getting in.

Anyhow, if you use caps, remember to put them 'across' the leads (parallel not series). One cap wire to positive, and one to negative. This will give the noise a path to ground and leave the clean dc current alone. You just need to use a big enough cap to trap all the noise. The formula is Xc=1/(2*pi*freq*C) and you want Xc (in ohms) to be lower than the power input resistence for the 'lowest' expected freq of the noise (since caps are known as high-pass filters). 'C' is in Farads. pi is 3.141592654...

 

Depends on the quality coax you use. Coax is suppposed to block signals, but I have seen many types that are not braided as tight as others. I broke a coax on vacation last year and had to use a K-Mart magnetic antenna to get home on. Had problems with the coax the rest of the way home. I still use the magnetic base for my antenna, but have replaced the coax that came with it to a better quality. I have no more problems and still have flat SWR.

 

Cobra, what does that Ford part look like? I am trying to go the cheap route and pick up a power filter from radio shack. If i can't get a power filter i might even try a capacitor.

 

Here are a few
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CT LG%5F002%5F001%5F019%5F008&product%5Fid=270%2D030
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CT LG%5F002%5F004%5F004%5F000&product%5Fid=15%2D579
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CT LG%5F002%5F001%5F019%5F008&product%5Fid=270%2D055

This is probably what they look like on the inside
http://www.filterconcepts.com/dc/ds_series.html
http://www.filterconcepts.com/dc_filters.html

Just a simple crossover circuit, capacitors and coils.